Document Detail

Use of opposing reflex stimuli and heart rate variability to examine the effects of lipophilic and hydrophilic beta-blockers on human cardiac vagal control.
MedLine Citation:
PMID:  10545309     Owner:  NLM     Status:  MEDLINE    
Evidence from animal studies suggests that beta-blockers can act within the central nervous system to increase cardiac vagal motoneuron activity. We have attempted to determine whether such an effect is evident in healthy humans, by examining the effects of lipophilic and hydrophilic agents on heart rate variability and cardiac vagal reflexes. A total of 20 healthy volunteers took part in the study. Autonomic studies were performed after 72 h of treatment with placebo, atenolol or metoprolol in a blinded cross-over design. ECG recordings were taken at rest and during mental and orthostatic stress. Heart rate variability was measured in the time and frequency domains. The effects on heart rate of two opposing cardiac vagal reflexes were examined. Trigeminal stimulation causing vagal stimulation, and isometric forearm muscle contraction ('muscle heart reflex') causing vagal inhibition, were performed alone and simultaneously. At rest, during mental stress and during trigeminal stimulation, beta-blocker therapy was associated with significantly increased high-frequency beat-to-beat heart rate variability when compared with placebo. There were no significant differences in effects on heart rate or heart rate variability between atenolol and metoprolol. Analysis of the muscle heart reflex, alone and with simultaneous trigeminal stimulation, showed that the magnitude of the R-R interval response was significantly greater after beta-blocker therapy compared with placebo, but the effects of atenolol and metoprolol were equivalent. beta-Blocker therapy increased cardiac vagal activity, as shown by measures of high-frequency heart rate variability and reflex studies. Lipophilic and hydrophilic beta-blockers appeared to be equally efficacious in increasing the cardiac vagal modulation of heart rate.
J C Vaile; J Fletcher; M Al-Ani; H F Ross; W A Littler; J H Coote; J N Townend
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Publication Detail:
Type:  Clinical Trial; Journal Article; Randomized Controlled Trial; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Clinical science (London, England : 1979)     Volume:  97     ISSN:  0143-5221     ISO Abbreviation:  Clin. Sci.     Publication Date:  1999 Nov 
Date Detail:
Created Date:  2000-01-12     Completed Date:  2000-01-12     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  7905731     Medline TA:  Clin Sci (Lond)     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  585-93; discussion 609-10     Citation Subset:  IM; S    
Departments of Cardiovascular Medicine and Physiology, University of Birmingham, Edgbaston, Birmingham B15 2TH, U.K.
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MeSH Terms
Adrenergic beta-Antagonists / pharmacology*
Atenolol / pharmacology
Baroreflex / drug effects*,  physiology
Cross-Over Studies
Double-Blind Method
Electric Stimulation
Electrocardiography / drug effects
Heart Rate / drug effects*
Metoprolol / pharmacology
Parasympathetic Nervous System / drug effects,  physiology
Trigeminal Nerve / physiology
Vagus Nerve / drug effects*,  physiology
Reg. No./Substance:
0/Adrenergic beta-Antagonists; 29122-68-7/Atenolol; 37350-58-6/Metoprolol
Comment In:
Clin Sci (Lond). 1999 Nov;97(5):609-10   [PMID:  10545312 ]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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